Effect of Bt cotton on nutrient dynamics under varied soil type

Since transgenic cotton was first grown commercially in India in 1996, the areas cultivated have increased rapidly around the world. Bt cotton is produced by inserting a synthetic version of a gene from the naturally occurring soil bacterium Bacillus thuringiensis into cotton. Bt cotton may affect nutrient dynamics in many ways during its life-span with regard to the temporal-spatial relevance of Bt proteins. Given this, we aimed to evaluate nutrient availability under both Bt and non-Bt systems and varied soil type. The study was conducted during the 2010 wet season (July to December) in a net-house at the Institute of Agricultural Sciences of Banaras Hindu University. It was carried out on three different soil orders i.e. entisol, inceptisol and alfisol. Bt-cotton (cvNCS-138) and its non-transgenic isoline (cvNCS-138) were grown until maturity. A no crop pot was maintained with three replications for all the three soil orders. Study design was a factorial experiment under a completely randomized block design with three replications. The study concludes that available N was reduced by 12-13% under Bt-cotton compared to non-Bt isoline and no crop treatment whereas it showed a significant increase in available P in the soil under Bt-cotton (7.8% increase) compared to non-Bt isoline and no crop treatment. Furthermore, it has been observed that available K value varied from 82.88 kg ha-1 to 76.88 kg ha-1 in the soil under Bt-cotton and from 90.33 kg hato-1 83.55 kg ha-1 in the non-Bt crops and a significant increase in the Avalaible Zn in the soil under Bt-cotton compared to non-Bt isoline and no crop treatment.